Migration is the dominant project here, and it carries more risk than any other Shopify app migration. Scope it properly.
For migrations, ask about the staging plan first. Active subscriptions carry payment tokens, next-billing dates, discount states and histories. Everything has to arrive intact or customers get double-billed, missed, or cancelled without asking. The only safe approach is a test cohort migrated and verified across a full billing cycle before the rest follow. A specialist who proposes moving everyone at once is telling you they haven't been burned yet. Migrations run $3,000-$20,000 depending on subscriber count.
Never migrate into a peak billing week or Q4. Subscription billing is concentrated on particular dates, and a migration landing near one turns a manageable problem into a support crisis.
Treat cancellation flow design as its own engagement. This is where Loop earns its keep, and it's a design and offer-strategy job rather than configuration. The flow needs different responses to different cancellation reasons — too expensive, too much product, not using it, quality issue — because a blanket discount offer wastes margin on people who were leaving for reasons a discount doesn't address. Runs $2,000-$8,000.
Ask what they measure. A subscription specialist who talks about subscriber count without talking about churn rate, average subscription length, or revenue retention is measuring the wrong thing. Ask which numbers they'd expect to move and by when.